1. Field of the Invention
The present invention relates to a receiver for digital broadcast such as cable broadcast, and more particularly, to a receiver that implements various functions based on a pre-installed application and a downloaded application.
2. Related Art
In recent years, digitization has proceeded also in cable broadcast which provides various services. For a receiver for such cable broadcast, various techniques have been developed (see, for example, JP 2006-511106 A (WO 2004/051401)). OCAP (Open Cable Application Platform) has been proposed as a next-generation North American cable broadcast standard.
According to the OCAP, a receiver such as an STB (set-top box) can download various applications (Java applications) such as an electronic program guide (EPG) and an application for viewing VOD (Video on Demand) from a broadcast station and executes the downloaded applications based on an API (Application Program Interface) defined in the OCAP standard, achieving predetermined functions. Namely, the receiver only operates based on the predetermined API and does not recognize specific functions that are implemented by the downloaded applications.
Such a receiver checks, when the power is turned on, whether downloaded applications, and so on, which are periodically transmitted from a broadcast station, have been delivered. If a downloaded application has been delivered, the receiver executes the downloaded application.
The receiver holds an application (hereinafter, referred to as a “pre-installed application”) that is originally installed thereon, in addition to a downloaded application transmitted from the broadcast station. When the receiver does not have any downloaded applications, the receiver performs a function according to the pre-installed application.
A downloaded application and the pre-installed application may provide the same function. Such case causes confusion for a user operation, or an operational malfunction since the downloaded application and the pre-installed application may affect each other in resource control. This is not desirable. In such a case, the receiver needs to make the following various adjustments of between control by the pre-installed application and control by the downloaded application:                Control of obtaining of a remote control key;        Display control of a common function between menus;        Exclusive control between resources;        Control of activation of an application.        
Further, in the receiver, when data communication is performed by both the downloaded application and a cable card, a plurality of IP addresses and a plurality of MAC addresses need to be processed and thus there is a problem that the process cannot be done with only one ether chip.